Along with Saudi Arabia and Venezuela, Canada has one of the world's major hydrocarbon resources. The Canadian resource, estimated to contain as much as 1.7 trillion barrels of heavy oil or bitumen, is largely found in the province of Athabasca in the form of oil sands.
Oil sands are a mixture of sands and other rock materials and contain crude bitumen. Currently about 1.5 million barrels of oil per day are generated from Canadian oil sands and much of that is transported to the United States for upgrading.
The majority of the oil sands processing is a combination of strip mining and a water-based extraction. Hugh quantities of water (2-4 barrels per barrel of oil) are required to obtain a single barrel of oil from the oil sands.
Oil sands companies are currently held to a zero-discharge policy by the Alberta Environmental Protection and Enhancement Act (1993). Thus, all oil sands process water produced must be held on site. This requirement has resulted in over a billion cubic meters of tailings water held in containment systems. Those that produce the tailings water have been held responsible for reclaiming the water and finding a way to release the reclaimed water back into the local environment.
Despite extensive programs that have led to significant improvements including up to 90+% use of recycled water, the tailings ponds and buildup of contaminants in the recycled water and in tailings ponds represent what is considered to be a fundamentally non-sustainable process.
Waterless approaches using hydrocarbon solvent extraction technology have been examined. These approaches offer a pathway to obtaining oil from oil sands that could be potentially low energy, water free, and environmentally superior to the current water-based technology.
U.S. Pat. No. 3,475,318 to Gable et al. is directed to a method of selectively removing oil from oil sands by solvent extraction with subsequent solvent recovery. The extraction solvent consists of a saturated hydrocarbon of from 5 to 9 carbon atoms per molecule. Volatile saturated solvents such as heptane, hexane and non-aromatic gasoline are used to selectively remove saturated and aromatic components of the bitumen from the oil sand, while leaving the asphaltenes on the sand. In order to remove the asphaltenes for process fuel, aromatic such as benzene or toluene is added to the solvent at a concentration of from 2 to 20 weight percent.
U.S. Pat. No. 4,347,118 to Funk et al. is directed to a solvent extraction process for tar sands, which uses a low boiling solvent having a normal boiling point of from 20° C. to 70° C. to extract the bitumen from the tar sands. The solvent is mixed with tar sands in a dissolution zone at a solvent:bitumen weight ratio of from about 0.5:1 to 2:1. This mixture is passed to a separation zone containing a classifier and countercurrent extraction column, which are used to separate bitumen and inorganic fines from extracted sand. The extracted sand is introduced into a first fluid-bed drying zone fluidized by heated solvent vapors, to remove unbound solvent from extracted sand and lower the water content of the sand to less than about 2 wt. %. The treated sand is then passed into a second fluid-bed drying zone fluidized by a heated inert gas to remove bound solvent. Recovered solvent is recycled to the dissolution zone.
U.S. Pat. No. 7,985,333 to Duyvesteyn is directed to a method for obtaining bitumen from tar sands. The method includes using multiple solvent extraction or leaching steps to separate the bitumen from the tar sands. A light aromatic solvent such as toluene, xylene, kerosene, diesel (including biodiesel), gas oil, light distillate, commercially available aromatic solvents such as Solvesso 100, 150, and 200, naphtha, benzene and aromatic alcohols can be used as a first solvent. A second hydrocarbon solvent, which includes aliphatic compounds having 3 to 9 carbon atoms and liquefied petroleum gas, can also be used in the extraction process.
U.S. Patent Pub. No. 2009/0294332 to Ryu discloses an oil extraction process that uses an extraction chamber and a hydrocarbon solvent rather than water to extract the oil from oil sand. The solvent is sprayed or otherwise injected onto the oil-bearing product, to leach oil out of the solid product resulting in a composition comprising a mixture of oil and solvent, which is conveyed to an oil-solvent separation chamber.
U.S. Patent Pub. No. 2010/0130386 to Chakrabarty discloses the use of a solvent for bitumen extraction. The solvent includes (a) a polar component, the polar component being a compound comprising a non-terminal carbonyl group; and (b) a non-polar component, the non-polar component being a substantially aliphatic substantially non-halogenated alkane. The solvent has a Hansen hydrogen bonding parameter of 0.3 to 1.7 and/or a volume ratio of (a):(b) in the range of 10:90 to 50:50.
U.S. Patent Pub. No. 2011/0094961 to Phillips discloses a process for separating a solute from a solute-bearing material. The solute can be bitumen and the solute-bearing material can be oil sand. A substantial amount of the bitumen can be extracted from the oil sand by contacting particles of the oil sand with globules of a hydrocarbon extraction solvent. The hydrocarbon extraction solvent is a C1-C5 hydrocarbon. The particle size of the oil sand and the globule size of the extraction solvent are balanced such that little if any bitumen or extraction solvent remains in the oil sand.
U.S. Patent Pub. No. 2012/0261313 to Diefenthal et al. is directed to a process for producing a crude oil composition from oil sand that uses a solvent comprised of a hydrocarbon mixture. The solvent is injected into a vessel and the oil sand is supplied to the vessel such that the solvent and oil sand contact one another in the vessel, i.e., contact zone of the vessel. The process is carried out such that not greater than 80 wt % of the bitumen is removed from the supplied oil sand, with the removal being controlled by the Hansen solubility blend parameters of the solvent and the vapor condition of the solvent in the contact zone. The extracted oil and at least a portion of the solvent are removed from the vessel for further processing as may be desired.
U.S. Patent Pub. No. 2013/0220890 to Ploemen et al. is directed to a method for extracting bitumen from an oil sand stream. The oil sand stream is contacted with a liquid comprising a solvent to obtain a solvent-diluted oil sand slurry. The solvent-diluted oil sand slurry is separated to obtain a solids-depleted stream and a solids-enriched stream. The solvent-to-bitumen weight ratio (S/B) of the solids-enriched stream is increased to produce a solids-enriched stream having an increased S/B weight ratio and a liquid stream. The solids-enriched stream having an increased S/B weight ratio is filtered to obtain the bitumen-depleted sand. The solvent can include aromatic hydrocarbon solvents and saturated or unsaturated aliphatic hydrocarbon solvents.
There is a continuing need for waterless approaches using hydrocarbon solvent extraction technology to extract crude oil and bitumen products from oil sand. There is a particular need for obtaining high quality crude oil and obtaining relatively dry tailings from the hydrocarbon extraction processes.